Mystery booms
Along with the contrails reported, there were anomalous sonic boom signatures recorded by Caltech.
This report maps the sonic booms from the Space shuttle and the SR71. It also confirms the Mach number your co-worker stated.
On page 27 section5 it details the analysis of the "mystery booms". They were originally said by the Air force to be two booms simultaneously created by a pair of F-4 Phantoms.
Caltech came up with a much more plausible explanation.
They were "blown in" from offshore maneuvers and thus distorted.
(Yeah right)